The overall goal of this Program Project is to develop novel effective and safe tuberculosis (TB) vaccine. The strategy taken is based on the results generated by the Jacobs laboratory, indicating that safe and effective TB vaccines can be derived from virulent Mycobacterium tuberculosis (Mtb): immunization with the markedly attenauted deltaRD1delta-panCD Mtb (generated by disruption of the a 10-kb genomic region called RD1 and the pantothenic acid biosynthetic genes, panC and panD) protects CD4 T cell-deficient mice against challenge with virulent bacilli in a CD8 T cell-independent manner. The granuloma plays a significant role in host defense against Mtb. Interaction between the host and the bacillus in the granuloma determines disease outcome and/or tissue-damaging immnunopathology, an undesirable feature of vaccine candidate in terms of safety that is caused by tumor necrosis factor (TNF). Understanding the host granulomatous response will help guide the design of anti-TB interventions including vaccines. Project 3 will direct efforts at i) characterizing the granulomatous response elicited by the Mtb mutant vaccines; ii) isolating mutants of the tubercle bacillus with diminished capacity to induce macrophage TNF production, so as to identify genes whose disruption will cause attenuated Mtb immunopathogenicity and therefore, enhances vaccine safety; iii) examining the granulomatous reaction of deltaRD1delta-panCD-immunized CD4-deficient mice, developed in response to challenge with virulent Mtb. We believe these studies will generate information that will guide the design of safer and more effective TB vaccines, and reveal novel host defense and immunopathologic mechanisms involved in tuberculous infection.